UI Design for Developers: Introduction

Designers vs. developers - it is an argument as old as computers. The truth is, though, neither can live without the other. A brilliant UI design is as worthless without functionality as is the best piece of code with an ugly, unusable frontend. In this first post on UI Basics for developers, I am going to try and lay out some simple ground rules that devs can follow to make sure their apps, templates and prototypes are as beautiful as the code itself - and usable to boot.

Think: the first impression is the last impression.

Alignment

Alignment refers to the position or orientation of an element in relation to another element or to itself. When we refer to two elements being aligned to each other, alignment usually refers to which side of both elements is in line. In the context of text, alignment refers to the side to which text is anchored in a straight line.

Form Design

In the image above, the second example of a simple form design shows labels that are right-aligned to each other with input fields that are left-aligned. This ensures that the association between each label and its input field is clear and the user does not get confused if some labels are too small while others are long.

Think: Make sure input fields are not too far away from the longest label. If the variation in width is small, try right-aligning labels and left-aligning input fields.

Text

For text, it is ideal to use left-alignment when desiging for the screen. Since most for-screen type rendering methods are incapable of distributing space appropriately when justifying text to both sides, left alignment keeps text readable and well organized. You can, of course, use center and right alignment where the design demands it, but those are usually reserved for special cases and smaller chunks of text.

Flow

The primary purpose of any user interface is to let the user interface with the application. This, believe it or not, is not going to be possible unless you tell the user what he needs to do and in what order. Since you won't be there behind every user to help them out with this, the interface needs to provide all the cues. Here are some questions to ask when evaluating whether the intended workflow is appropriate:

How critical is it that the task be performed in a set order of steps?

Is it obvious to the user where to start and what to do next?

Is the intended outcome stated or implied - implicitly, if not explicitly?

Let's take the example of a search category selection on iStockPhoto. In this case, I can either search everything or select a specific category to limit my searches to that type of information. Since the primary act is to enter a search term and hit Search, those should be fairly obvious. A possible step in between is to select a category, which can be a drop-down list between (you guessed it right) the search field and the Search button.

Another example is the income/expense input dialog in the cashbase app. The fields are arranged according to the typical workflow one will use to log such information: enter the amount (which is the most important element), select a category, add a note if necessary, and click Add. Secondary information that will be used much less frequently - like the date which by default is today, and the option to repeat or cancel - are available, but much more subtle.

Further reading:

Proximity

Related elements in an interface should be grouped together. This might sound like common sense when I mention it, but it is not always well understood. The reason all page navigation links on most websites are laid out in a single horizontal bar, is so that the user can identify the relationship at a glance and make the choice to interact with them without any confusion.

Let's look at this example from Gmail - an app that many of use on a regular basis. This is the toolbar that appears at the top when you open a mail. Although all those buttons perform some action on the open message, they are further grouped together based on what they do - actions one would use to get rid of the message (archive, spam, delete), to change the importance of the message (when using priority inbox), label-related actions, and finally a drop-down with secondary options.

Another example of good use of proximity is the options bar in Zootool. The toolbar at the bottom is divided into three sets, each corresponding to the three panes in the app: the list packs on the left, the mail window in the center which contains all your bookmarks, and the details pane on the right.

Further reading:

Hierarchy

Not everything in a user interface, or any layout for that matter, carries the same importance as everything else. Hierarchy is the arrangement of elements in a way that denotes what is higher in order, what comes next, and so on.

Let's look at this example here and try to identify what the order of precedence is. Since everything - titles, labels and paragraph text - looks the same, one has to read through everything to make sense. If the same interface was tweaked just a little bit like below, the overall impact on the readability and in turn the usability of the interface is enormous.

As a general rule, the page heading should be biggest and most visible on the screen. This is followed by section titles, sub-titles and then smaller labels. Paragraph text can be more or less prominent depending on its purpose. It is also not limited to text. Primary action buttons can be differentiated from secondary actions by making them brighter, bigger or fancier. Input fields for mandatory inputs can be made more obvious than the others. I could go on, but I think you get the idea.

Contrast

Another very important consideration when designing interfaces is to ensure clear differentiation between elements. Of course, you want the text to be readable on the background, but contrast goes beyond simply using light text on a dark background or vice versa. Headings and paragraph text should be clearly distinguishable. Panels and navigation bars need to be segregated from each other so the user knows what is what. The list goes on.

Contrast can be established using one or more of the following characteristics:

Color

This should be obvious, but its amazing how often people slip on this point. If your background is light, you obviously want the text to be dark to ensure readability. Although in theory complimentary colors should work well together, it is not always that easy. Try placing bright green text on a red background and you will know what I'm saying.

The possibilities here are limitless, so my first recommendation to anyone looking to select colors is to pick up a popular color palette from sites like Adobe Kuler or ColourLovers. They are contributed, evaluated and voted up by passionate users who usually know their way around color. All the basics of color matching and contrast are usually taken care of, so its just a matter of deciding which color scheme works in your app's context.

One note of caution though - be very wary of going overboard with color. You don't want them to overshadow the utility and usability of your app.

Size

Another good way to differentiate between elements - based on hierarchy, categorization, or visual flow - is to use different sizes. This applies to text as much as it does to images, backgrounds and static or interactive elements. You may want to put more emphasis on the primary action button, for example, and keep the secondary buttons comparatively less accessible. Or optional prompts can be smaller and lighter than the primary labels in a form.

The TeuxDeux app does a brilliant job of using color to differentiate between past, present and future days. Since the layout is geared towards a work week, different sizes of text are used to make sure that names of days are easy to identify, while the dates are comparatively more subtle.

Interaction

Since the primary purpose of any user interface is to enable users interact with the app, it is imperative that learners intuitively know what to do. As creators of the interface, it is very easy to forget that you won't be there for every user to tell them what to do. Neither do users have the patience any more to read manuals and quick start guides before diving into using an app. The interface is required to make it amply clear what parts of it are clickable, touchable, draggable - in short, interactive.

Everyone knows how to flick an electrical switch, right? The thing that makes it obvious to anyone that a switch needs to be pressed at a certain point to change state is called affordance. On the flat surface of a screen - desktop, mobile or otherwise - different techniques can be utilized to enable users intuitively click a button or type inside an input field. When creating text hyperlinks, adding an underline for the link is the most commonly used standard, although there are many other creative ways to do that.

Here are some examples:

Going with the switch example, how do you know if flicking the switch did what it was supposed to do? The light comes on or goes off, or in some cases a light inside the switch helps make it clear whether the switch is on or off.

In an application, such feedback can be very obvious in cases where a button navigates to another page or opens a popup, but what about situations where all it does is process some data in the background - like when saving changes to the user settings? Some sort of a feedback mechanism is critical to let users know their action was successful. This could be as simple as a "your settings were saved" message, a brief notification at the top of the page, or a quick highlight around the area that was updated.

When you add a new task in Remember the Milk, it can either appear in the list on the same page, or simply get added to another list in the background (if, for example, the task has been assigned to a different category). The feedback for the action is therefore provided at two levels:

a green highlight appears for a couple of seconds behind the task in the list to point to where it has been added, and

a very prominent message appears on a yellow background at the top of the page letting the user know what exactly happened.

Typography

The text in your app - everything from the logo to the titles, labels and copy - is your primary mode of communication with the users. Since it is how your users access information about the app or through it, how you set the type can mean the difference between success and failure. Of course titles have to be bigger than body text and the fine print has to be, well, fine; but a lot of other decisions also influence how users consume information.

Fonts

Step one: define your fonts. It surprises me how many developers simply never bother to change whatever font their text gets generated in. Default fonts change from OS to OS and browser to browser, which means that unless you explicitly state what font you want to use, your text is going to look different in every OS and browser combination. Besides, Times New Roman - which a lot of browsers still use as the default font - is just not a good font for on-screen reading. My first recommendation is often to use a sans-serif font, although Georgia or the new Cambria font in Windows 7 also look good.

If you decide to use fonts other than the safe, universally available ones like Arial/Helvetica, Georgia, Tahoma etc., make sure there is a way to have them render similarly on all platforms. If Flash is your development environment of choice, embed them where necessary. For HTML/JS based apps, use @font-face in CSS or any of the web font services like Typekit or Google WebFonts. Remember though, that these techniques come with a caveat of extra file sizes for the embedded fonts. If speed and responsiveness are paramount for you, sticking to the base fonts is your best bet.

Disclaimer: Yes, I do know that Arial and Helvetica are not exactly similar, but they are similar enough for most users to not notice the difference.

Leading

The amount of space between two lines of text is the leading. You want the leading of your paragraph text (line-height in CSS speak) to be at least 140% of the font size to make sure it is easily readable. Any less and your text is going to be much harder to read and - more imporantly - to scan through.

Localization

If you plan to translate your app into oither languages - and you really should - it is best to test the interface early on with different scripts. At the very least, the amount of space a certain message requires can vary drastically across different scripts. The East Asian scripts use fewer words on an average but need a bigger font size, Indian (Indic) scripts also need to be slightly bigger to be readable and middle-eastern scripts (like Arabic) go from right to left instead of the usual left-to-right.

Wrapping Up

That's about it for now. I hope these tips covered enough basics for you to start applying them in your projects right away. As with most design-related disciplines, there are no hard and fast rules to follow, and everyone has their own take on how things should work. So if you disagree with any of my suggestions above - or even if you agree with them but have a different perspective - let's hear about them in the comments.

Next up, we will take all of this wisdom and try applying it to an actual interface. Stay tuned!

I'm a graphic designer, technology enthusiast and gamer. Other than drooling over gadgety goodness on the web and elsewhere, I work as a design consultant and entrepreneur with a focus on web, communication design and learning design.